It is well known that thermal and photochemical yellowing are major concerns in magenta image stability of color prints. Over the years improvement in magenta image stability has been achieved by introducing more efficient image stabilizers. However, there still exists a need to further improve the resistance to yellowing in color paper.
It has been known for some time that compounds having the generic structure S are able to undergo reaction with residual magenta coupler and thereby effectively prevent both thermal and photochemical yellowing since the products of the reaction are not yellow and are not prone to yellowing. However, a major problem in the utilization of these compounds is the loss of coupler during storage of the photographic element prior to exposure and processing resulting in a reduction in color density in the print. See for example, U.S. Pat. No. 4,540,657 to Krishnamurthy and Japanese Patent Publication No. 62-131259 to Fuji Photo Film Co., Ltd. The generic structure of Compound S is represented below: ##STR4## wherein: A is a polyvalent atom, an acidic oxide group, a carboxylic group, a heterocyclic moiety, a carbocyclic group, or an alkane or substituted alkane group; each L is at least one divalent linking group; R.sub.1 and R.sub.2 are H, alkyl, cycloalkyl, aryl, heterocyclic, ester; n is a positive integer with a range of 1-6; m is a positive integer of at least one; with the proviso that at least one of A, L, R.sub.1 or R.sub.2 contains at least one ester or amide group derived from an acidic oxide of carbon, phosphorous, sulfur, boron or silicon.
In copending, commonly assigned application U.S. Ser. No. 08/000,431, filed Jan. 4, 1993, the disclosure of which is hereby incorporated by reference, we showed that the compound S-1 (having the structural formula set forth below) could be incorporated in a silver halide color photographic element containing a ballasted magenta coupler such that there is negligible loss of coupler prior to processing. This was achieved by coating the epoxy compound in separate layers that were adjacent to the imaging layer containing the magenta coupler and the green sensitized emulsion. Furthermore, it has also been demonstrated that mixing of S-1 with residual magenta coupler after processing may be achieved by using a pH dependent solubilizing agent, e.g., a fatty acid, such as myrisitic acid, in the coating and processing the coating using developer which preferably contains benzyl alcohol. However, the use of benzyl alcohol in the developer raises environmental concerns. ##STR5##
In an effort to eliminate the use of compounds such as benzyl alcohol to achieve post process mixing of the epoxy scavenger with the residual magenta coupler, copending, commonly assigned U.S. Ser. No. 08/255,512, filed Jun. 8, 1994, the disclosure of which is hereby incorporated by reference, discloses novel terminal epoxy compounds containing a pH-dependent solubilizing moiety in the molecule. Dispersions of these compounds are coated in layers adjacent to the magenta imaging layer, and the compounds diffuse into the magenta layer upon processing where they react with residual magenta coupler yielding products that are not yellow or prone to yellowing. The approach is effective in reducing thermal and photochemical yellowing in processed prints without the use of benzyl alcohol.
Problems have been discovered, however, when these epoxy compounds are used in combination with many conventional compounds which are used as light stabilizers for magenta image dyes. It has been found that such dye image stabilizers severely inhibit the post-process reaction between residual magenta coupler and the terminal epoxy compounds and thereby suppress the beneficial effects of the epoxy compounds on yellowing.
It is therefore desired to combine the epoxy compounds with image stabilizers for the magenta image dye such that there is little or no inhibition of the post-process reaction between the epoxy compound and residual magenta coupler. Furthermore, it is desired to use residual magenta coupler scavenger epoxy compounds to obtain excellent image stability in terms of both dye fade and yellowing.